如何返回代碼的開頭/具有嵌套循環？

Question

我希望運行我的代碼，以便如果不滿足條件（在if循環中），它將返回到代碼的開頭，要求用戶輸入另一句。 如何添加此嵌套循環（如果這就是所謂的）？

sentence = input("Please input a sentence: ")
word = input("Please input a word: ")
sentence = sentence.lower()
word = word.lower()
wordlist = sentence.split(' ')
print ("Your word, {0}, is in positions:".format (word))
for position,w in enumerate(wordlist):
    if w == word:
        print("{0}".format(position+1))

Answer 1

您可以在代碼周圍放置while循環，然后根據輸入break或continue ：

while True:
     sentence = input("Please input a sentence: ")
     if bad(sentence): # replace with actual condition
         continue
     ...
     for position, w in enumerate(wordlist):
         ...
     break

Answer 2

做就是了：

while True:
    sentence = input("Please input a sentence: ")
    if sentence.lower() == "quit": break
    word = input("Please input a word: ")
    sentence = sentence.lower()
    word = word.lower()
    wordlist = sentence.split(' ')
    print ("Your word, {0}, is in positions:".format (word))
    for position,w in enumerate(wordlist):
        if w == word:
            print("{0}".format(position+1))